Mixed Precipitation Signals: May 2011and a Spring 2011 Overview

Dr. David A. RobinsonNew Jersey State ClimatologistCenter for Environmental Prediction, School of Environmental and Biological
Sciences/NJAES, Rutgers UniversityJune 6, 2011

May Overview

A dismal mid-month period left many believing that May was a rather wet month. Truth be told, this depends on where you reside in the state, as some northern areas were almost twice as wet as average while the extreme south had just over half of average precipitation. The preliminary statewide average is 3.67". This is 0.63" below average, but somewhat above the median at 52nd wettest of the past 117 years. Morris County led the way with 8.19" and 8.10" received at two CoCoRaHS stations in Rockaway Township. Elsewhere in the county, Harding Township totaled 8.16", Boonton 7.94" Morris Township 7.91" and two Denville stations came in at 7.85" and 7.78". Totals fell off to near average levels in central NJ. In the far south, Upper Deerfield (Cumberland County) only received 1.96" and in Cape May County, Sea Isle City had 2.26" while Middle, Lower and Upper Townships caught 2.33", 2.36" and 2.37", respectively.

The first rain of the month fell in the northwest corner of the state on the 3rd. In Sussex County, Montague received 0.67", High Point 0.42" and Walpack 0.37". All of the state caught at least 0.25" on the 4th with southern coastal areas seeing as much as 1.20", with 1.13" at two Berkeley Township (Ocean) locations and 1.12" in Woodland Township (Burlington).

Conditions were quite dry from the 5th through the 13th before persistent clouds accompanied by off and on rain of varying intensities arrived on the 14th. Before conditions began to brighten and dry out on the 24th, as much as 6.45" and 6.47" had fallen at two Rockaway Township (Morris) locations. Of the 113 CoCoRaHS stations that reported on all of the nine days between the 14th and 24th, 13 received between 5.00" and 6.47", 19 caught from 4.00" to 4.99", 28 had 3.00" to 3.99", and only Wildwood Crest (Cape May) with 0.71" came in under an inch. Notable totals during this period included 4.40" at Harding Township (Morris) and 4.39" in Morris Township from the 14th to 17th.

It is difficult to subdivide totals during that period, as rains frequently came and went across NJ. However a late afternoon thunderstorm on the 15th deposited pea-size hail in Washington Township (Mercer). Wires were reported down from strong winds in Fredon Township (Sussex). Localized rains of close to 2.00" in two hours on the 16th led to flash flooding of basements, roads and streams in Bernards Township in northern Somerset County.

Late on the 18th Harrison (Hudson) saw 2.35", Saddle Brook (Bergen) 2.23" and Boonton (Morris) 2.14". A severe late afternoon thunderstorm on the 19th was concentrated in west central counties. Two stations in Liberty Township (Warren) reported hail the size of grapes and even some stones the size of golf balls, with grape size (approx. 1/2") in Franklin Township (Warren). Rain totaled 1.82" in Washington (Warren) and 1.68" at Holland Township (Hunterdon). This precipitation, on top of rains of previous days, led to flooding of streams and roads in Warren and Hunterdon counties. Later that evening, Woodbine (Cape May) received pea-size hail.

The north coast saw the most rain on the 20th with three Brick Township (Ocean) stations measuring 0.95", 0.89" and 0.83". The northern tier received most on the 21st, with 0.54" in Hawthorne (Passaic) and 0.46" at Wantage (Sussex). The episode ended with the northern half of the state getting wet on the 23rd, especially Warren County, where Washington received 1.84" and White Township 1.70". Flash flooding occurred as a result of the one hour downpour and trees were reported down in southeast Warren County.

Overall, during this damp period, thunderstorms occurred somewhere in the state on the 15th to 19th, the 21st and 23rd. Heavy fog appeared at times on the 16th (Ocean and Cape May), 19th (Cape May), 21st (Hunterdon and Camden), 22nd (Morris), 23rd (Warren) and 24th (Hunterdon and Mercer). The persistent heavy rain in the Highlands region resulted in the Passaic River in Little Falls (Passaic) cresting several inches above flood stage on the 20th and 21st, the third consecutive month that flooding occurred in the central Passaic basin. The Rockaway River at Boonton crested just over a foot above flood stage early on the 20th when the Ramapo River at Mahwah just reached flood stage.

The northwest corner was clipped with thunderstorms on the 26th, with 0.63" in Allamuchy Township (Warren) and 0.58" at Andover Township. Hail as large as 1.5" in diameter pelted Milford (Hunterdon), with pea-size hail in Greenwich Township (Warren), while trees were reported down in the Warren County communities of Allamuchy Township, Independence Township and Washington. Thunderstorms on the 28th brought central Jersey as much as 0.41" in Franklin and Montgomery Townships in Somerset County. Two other Montgomery stations caught 0.32" and 0.24". Early morning thunderstorms on Memorial Day (30th) deposited 0.61" in Hackettstown (Warren) and 0.41" in Rockaway Township (Morris), Mt. Olive (Morris) and Little Falls (Passaic).

Other than tree- and wire-felling winds in isolated severe thunderstorms during May, particularly in Warren County, it was not too windy a month. Gusts exceeding 40 mph were only observed on the 4th and 5th at Wantage (Sussex; 47 mph and 44 mph respectively) and the 30th at High Point Monument (Sussex; 42 mph). Overall, the 5th was the windiest day, with a dozen NJWxNet stations gusting between 30 and 37 mph. The highest barometric pressures of May were between 30.35" and 30.40" on the 1st and 2nd, and lowest at 29.45" to 29.50" on the 15th.

The preliminary statewide average May temperature of 63.4° was 2.9° above average and ranked as the 12th warmest since 1895 (Table 1). This continues an almost unbroken streak of above average months, with 13 of the past 15 falling into that category.

Rank

Year

May Temp.

1

2004

66.2°

2

1991

66.1°

3

1944

65.1°

4

1896

64.9°

5

1965

64.4°

6

2010

64.2°

7

1911

64.1°

7

1918

64.1°

9

1942

64.0°

10

1959

63.9°

11

1998

63.7°

12

2011

63.4°

12

1986

63.4°

14

1975

63.3°

15

2007

63.2°

Table 1. The 15 warmest Mays across New Jersey since 1895.

Despite the overall warmth, the first half of the month provided a few cool days with chilly mornings. The temperature fell to 31° at Berkeley Township (Ocean) and 32° at Walpack (Sussex) on the 1st. The 6th had the coldest morning of the month, with Walpack at 29°, Berkeley Township and Pequest (Warren) at 30° and Oswego Lake (Burlington) at 32°. The warm spot was West Cape May (Cape May), with a low of 54°. The last freeze of the season occurred at Walpack (32°) on the 10th, seven months to the day from the first freeze in NJ back in October 2010. The warmest morning of the month was the 30th, when Walpack (62°) was the coolest spot and Bivalve (Cumberland; 71°) the warmest.

With a rather cool start to May and then the persistent clouds of mid month, the first heat of the month did not arrive until the last week. The 26th brought the first 90° maximum temperatures to the state, with Sicklerville (Camden) coming in at 92° and nine other NJWxNet stations at 90° or 91°. The next day saw Hillsborough (Somerset) at 90°. The Memorial Day weekend was quite summer like, with temperatures in the 80°s most places, topping out at 93° in Sicklerville and Woodbine (Cape May) on the 30th and between 90°-92° at seven other locations. The monthly maximum of 95° was reached at Sicklerville on the 31st, with Upper Deerfield coming in at 93° and eight other spots at 90° or 91°.

Spring Overview

The spring season brought warmth and an abundance of rain to New Jersey. The preliminary average temperature of 52.9° was 2.2° above average. This ranks as the 10th warmest since 1895, with seven of the top 13 occurring in the past 21 years (Table 2).

Rank

Year

Spring Temp.

1

2010

55.3°

2

1921

54.7°

3

1991

54.0°

4

1945

53.9°

5

1977

53.7°

5

2004

53.7°

7

1998

53.5°

8

1903

53.2°

9

1985

53.1°

10

2011

52.9°

11

2000

52.8°

12

1946

52.7°

13

2002

52.6°

14

1955

52.4°

14

1942

52.4°

Table 2. The 15 warmest springs across New Jersey since 1895.

Spring 2011 brought a preliminary statewide average precipitation of 15.04". This is 2.64" above average and the 15th wettest on record (Table 3). Most of the precipitation fell as rain, although several March snow events deposited as much as 16.0" in Rockaway Township (Morris) and 13.9" at Blairstown (Warren). Rockaway came away the "winner" in the precipitation department as well, with two CoCoRaHS stations reporting totals of 25.97" and 24.62". Other hefty seasonal totals included the Morris County townships of Mine Hill (24.19"), Harding (24.17") and Randolph (23.91"). Conversely, conditions were dry for the season in extreme southern sections. Cape May County totals were as low as 8.16" in Wildwood Crest, with other locations coming in at 8.35" (Dennis Township), 8.90" (Middle Township), 9.44" (Lower Township) and 9.50" (Sea Isle City). Maximum seasonal totals from CoCoRaHS or NWS Cooperative stations with complete records in the 21 counties are shown in Table 4. With the arrival of summer, the abundant spring precipitation in northern counties has elevated reservoirs, ground water and streamflow to normal or above normal status. Such is not the case in southern areas; however there is no major concern of water deficits at this time.

Rank

Year

Spring Prcp

1

1983

22.25"

2

1984

20.03"

3

1953

18.11"

4

1952

17.76"

5

1940

16.76"

6

1989

16.59"

7

1998

16.00"

8

1901

15.87"

9

1980

15.71"

10

1958

15.50"

11

2010

15.36"

12

1948

15.28"

13

1973

15.16"

14

2007

15.15"

15

2011

15.04"

16

1912

14.90"

17

1933

14.57"

18

1990

14.22"

19

1947

14.00"

20

1961

13.99"

Table 3. The 20 wettest springs across New Jersey since 1895.

County

Location

Spring Prcp

Atlantic

Buena Vista Township

12.60"

Bergen

Saddle Brook

21.16"

Burlington

Medford Township

14.41"

Camden

Somerdale

13.78"

Cape May

Woodbine

11.17"

Cumberland

Vineland

13.50"

Essex

Newark Airport

16.48"

Gloucester

Franklin Township

13.67"

Hudson

Harrison

17.94"

Hunterdon

Franklin Township

21.07"

Mercer

Pennington

16.55"

Middlesex

North Brunswick Township

16.33"

Monmouth

Eatontown

13.54"

Morris

Randolph Township

23.91"

Ocean

Point Pleasant Beach

12.57"

Passaic

West Milford Township

24.65"

Salem

Woodstown

12.54"

Somerset

Bedminster Township

19.17"

Sussex

Hardyston Township

22.73"

Union

New Providence

17.70"

Warren

Mansfield Township

19.90"

Table 4. Maximum spring 2011 precipitation by county for communities with complete records.